Clemens Rauer, Juan J Nogueira, Philipp Marquetand, Leticia González
{"title":"Stepwise photosensitized thymine dimerization mediated by an exciton intermediate.","authors":"Clemens Rauer, Juan J Nogueira, Philipp Marquetand, Leticia González","doi":"10.1007/s00706-017-2108-4","DOIUrl":null,"url":null,"abstract":"<p><strong>Abstract: </strong>Cyclobutane thymine dimerization is the most prominent DNA photoinduced damage. While the ultrafast mechanism that proceeds in the singlet manifold is nowadays well established, the triplet-state pathway is not completely understood. Here we report the underlying mechanism of the photosensitized dimerization process in the triplet state. Quantum chemical calculations, combined with wavefunction analysis, and nonadiabatic molecular dynamics simulations demonstrate that this is a stepwise reaction, traversing a long-lived triplet biradical intermediate, which is characterized as a Frenkel exciton with very small charge-transfer character. The low yield of the reaction is regulated by two factors: (i) a relatively large energy barrier that needs to be overcome to form the exciton intermediate, and (ii) a bifurcation of the ground-state potential-energy surface that mostly leads back to the Franck-Condon region because dimerization requires a very restricted combination of coordinates and velocities at the event of non-radiative decay to the ground state.</p><p><strong>Graphical abstract: </strong></p>","PeriodicalId":18766,"journal":{"name":"Monatshefte Fur Chemie","volume":"149 1","pages":"1-9"},"PeriodicalIF":1.7000,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1007/s00706-017-2108-4","citationCount":"13","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Monatshefte Fur Chemie","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.1007/s00706-017-2108-4","RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2017/12/4 0:00:00","PubModel":"Epub","JCR":"Q3","JCRName":"CHEMISTRY, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 13
Abstract
Abstract: Cyclobutane thymine dimerization is the most prominent DNA photoinduced damage. While the ultrafast mechanism that proceeds in the singlet manifold is nowadays well established, the triplet-state pathway is not completely understood. Here we report the underlying mechanism of the photosensitized dimerization process in the triplet state. Quantum chemical calculations, combined with wavefunction analysis, and nonadiabatic molecular dynamics simulations demonstrate that this is a stepwise reaction, traversing a long-lived triplet biradical intermediate, which is characterized as a Frenkel exciton with very small charge-transfer character. The low yield of the reaction is regulated by two factors: (i) a relatively large energy barrier that needs to be overcome to form the exciton intermediate, and (ii) a bifurcation of the ground-state potential-energy surface that mostly leads back to the Franck-Condon region because dimerization requires a very restricted combination of coordinates and velocities at the event of non-radiative decay to the ground state.
期刊介绍：
"Monatshefte für Chemie/Chemical Monthly" was originally conceived as an Austrian journal of chemistry. It has evolved into an international journal covering all branches of chemistry. Featuring the most recent advances in research in analytical chemistry, biochemistry, inorganic, medicinal, organic, physical, structural, and theoretical chemistry, Chemical Monthly publishes refereed original papers and a section entitled "Short Communications". Reviews, symposia in print, and issues devoted to special fields will also be considered.
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